text = "To be or not to be,that is the question."

letters_set = set()
letter_count = {}

for char in text:
    if char.isalpha():
        letters_set.add(char.lower())

        if char.lower() in letter_count:
            letter_count[char.lower()] += 1
        else:
            letter_count[char.lower()] = 1

for letter in letters_set:
    count = letter_count[letter]
    print(f"{letter}:{count}")